The present invention relates to a process for joining differing kinds of synthetic resin to each other, and more particularly to a process for joining them using the heat of a laser beam.
In a first conventional process for physically joining synthetic resins, each of the synthetic resins has a contact surface thereon. A metal mesh is disposed on the contact surfaces of the synthetic resins, and the mesh is sandwiched between both of the synthetic resins. When the mesh is heated, both of the contact surfaces of the synthetic resins are melted by the heat of the mesh. Pressure then is applied to the outsides of the synthetic resins to press them together, and the synthetic resins are cooled. As a result of this first conventional process, one of the synthetic resins is joined to the other of the synthetic resins.
In this first conventional process, both synthetic resins normally are the same kind of synthetic resins so that both will have the same melting point, and so that they will blend easily into one another. If different kinds of synthetic resins are used, they may have differing melting points and may not blend easily into one another.
Further, in the first conventional process, a connecting wire is disposed between both of the contact surfaces of the synthetic resins to supply electricity to heat the mesh. Connecting the wire to the mesh between the synthetic resins requires an undesirably high amount of manual labor.
In a second conventional process for chemically joining synthetic resins, each of the synthetic resins has a contact surface thereon, and a bonding compound is disposed between both of the contact surfaces of the synthetic resins. The bonding compound normally is solid and is melted by heat, typically produced by applying high frequency or supersonic waves to the bonding compound. These waves also preferably melt the synthetic resins slightly to improve bonding. After a compressive force is applied to the synthetic resins, the synthetic resins are cooled. As a result of the second conventional process, one of the synthetic resins is joined to the other.
In the second conventional process, the synthetic resins again should be the same kind of synthetic resin, this time so that the bonding compound has the same adhesive properties for bonding to both synthetic resins. If different kinds of synthetic resins are used, the bonding compound may have differing adhesive properties as to the different kinds of synthetic resin. Accordingly, the adhesive strength of the bond to one kind of synthetic resin may be different from the adhesive strength of the bond to a different kind of synthetic resin, i.e., one bond may have a weak adhesive strength. Further, in the second conventional process with different synthetic resins, the synthetic resins may not both be melted by the heat of the high frequency or supersonic waves.
FIG. 11 shows a third conventional process for mechanically joining different kinds of synthetic resins. As shown in FIG. 11, a first plate 51 is mounted on a second plate 52. The first plate 51 is made of polypropylene resin, and the second plate 52 is made of polyethylene resin. The first plate 51 has a first hole 511, and the second plate 52 has a second hole 521 which is congruent with the first hole 511 of the first plate 51. A washer 54 is mounted on the first plate 51, and a screw 55 is inserted into a hole of the washer 54, the first hole 511 and the second hole 521. As a result, the first plate 51 is joined mechanically to the second plate 52.
However, in the third conventional process, the first hole 511 must be opened in the first plate 51, and the second hole 521 must be opened in the second plate 52. Then, the screw 55 must be inserted. Each of these steps is undesirably labor intensive. Further, the screw 55 projects from both of the first plate 51 and the second plate 52, marring the appearance of the final product. In addition, when tension is applied to the first plate 51 and the second plate 52 in the horizontal direction in FIG. 11, the first plate 51 or the second plate 52 may be torn at the first hole 511 or at the second hole 521, respectively.